1. Field of the Invention
The present invention relates to an internal combustion engine provided with a transmission which includes a transmission driving mechanism that shifts gears within the transmission to achieve a change in engine output speed, the transmission driving mechanism accomplishing shifting of gears within the transmission using an electric motor.
2. Description of the Background Art
It is known in the art to provide an internal combustion engine having a transmission with a transmission driving mechanism that executes the shift of the transmission gears. The known transmission driving mechanism achieves engine output speed change by shifting gears within the transmission using an electric motor. Such an internal combustion engine is disclosed, for example, in JP-A No. H11-82734.
The internal combustion engine disclosed in JP-A No. H11-82734 is mounted in an all terrain vehicle with a crankshaft directed in a longitudinal direction of the vehicle. In the corresponding transmission driving mechanism, the drive of an electric shift motor protruding from the front of a crankcase is transmitted to the turning of a shift spindle via a speed reducing device, the turning of the shift spindle turns a shift drum, moves a shift fork, the engagement of speed change gears in the transmission is changed, and a shift is executed.
A turning angle sensing device is attached to a front end of the shift spindle, the base of an arm is fitted onto its rear end, and an arm of a secondary spindle which is directed in a lateral horizontal direction perpendicular to the crankshaft and the left end of which is protruded on the side of the internal combustion engine is fitted to the end of the arm.
A hexagonal part is formed at the protruded left end of the secondary spindle, and the secondary spindle is turned by fitting a wrench onto the hexagonal part and rocking the hexagonal part. As a result, the shift spindle is manually turned via a fitting part of the aim, and the arrangement of speed change gears within the transmission can be shifted to achieve speed change. That is, the known transmission driving mechanism depends upon the secondary spindle to enable manual operation of the transmission using a tool such as a wrench when a shift by the electric shift motor is not performed.
As described above, in the transmission driving mechanism disclosed in JP-A No. H11-82734, since the transmission driving mechanism dedicated to manual operation using the secondary spindle is provided separately from the execution of a shift by the electric shift motor via the shift spindle, a large number of parts are required, the engine and transmission structure is intricate, the assembly thereof is troublesome, maintenance is required, and the cost is increased.
The present invention is made in view of the above described problems, and the object is to provide a transmission driving mechanism of an internal combustion engine in which a separate transmission driving mechanism for manual operation is not required, the number of parts is reduced, the structure is simple, no maintenance is required and the cost is reduced.